If you're looking for an easy way to upgrade your rental car on your next vacation, travel site Budget Travel suggests it's often as easy as booking the cheapest car available and hoping they run out.

It's a little counter intuitive, but the cheapest cars sell out first and the rental company has no choice but to upgrade you. That said, Budget Travel recommends you stay firm in not paying for an upgrade:

The check-in clerk may try to sell you an upgrade for a discounted fee. Say no. If they don't have the car you reserved, they usually give you a better model at no extra charge. Arrive early in the day, before most people return their cars, for the best shot.

It's not going to work every time of course, but some careful planning might turn that tiny sedan into something a bit more fun. Hit up the full post on Budget Travel for a few more tips for scoring free upgrades on your next vacation.